Cloning and characterization of a robust recombinant azoreductase from Shewanella xiamenensis BC01

Increasing interest in bio-treatment of azo dyes effluent requires more efforts on azoreductase exploration, which involves in the biodecolorization and bioremedimation. In this study, a full-length gene of 594 bp, azoR, encoding an aerobic azoreductase of 198 amino acids (designated as AzrS) was isolated from a Shewanella xiamenensis BC01. AzrS was heterologous recombinant into vectors of pET32a, pET28a or pET2Obl, and further expressed in E. coli BL21(DE3) for the first time. The optimal condition was achieved using the pET28a vector, as more than 90% protein was soluble (i.e., 278 mg/L). AzrS was an oxygen-insensitive, FMN-dependent, robust against to organic solvent and had extremely high activity with stability at room temperature. It occupied strong activities in multiple substrates as a ranking of methyl red > methyl orange > congo red, that was consistent with the results of molecular docking. In conclusion, AzrS showed good potential for bioremediation, due to its high over-expression in E. coli, non-sensitivity to oxygen, and with robust activity against metals and solvents. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.